1. Technical Field
The present invention relates to an electronic apparatus mounted with an electric motor and a method of controlling the electric motor mounted in the electronic apparatus.
2. Related Art
Generally, as an electronic apparatus mounted with an electric motor, a printing apparatus (which is also called “an ink jet printer”) which performs printing by ejecting ink on a printing medium (for example, a paper sheet) fed therein is known. Such a printing apparatus is provided with a motor (so-called sheet-feeding motor) for feeding the printing medium thereto, a motor (so-called carriage motor) for moving a printing head for ejecting ink, and the like. When these motors are intermittently driven, an amount of emitted heat becomes larger than an amount of discharged heat. Therefore, these motors may become overheated. Accordingly, such a printing apparatus is configured to perform emission heat controlling of controlling an amount of heat emitted by the respective motors if the amount of emitted heat calculated on the basis of a drive type of the respective motors exceeds a preset heat storage threshold value.
However, if power supply to the printing apparatus is interrupted from a power source (hereinafter, referred to as “a power-off state”), heat stored in the respective motors is gradually discharged. Therefore, in a case where the power-off state is relatively long (for example, the power-off state continues for one day or more), the heat of the respective motors is sufficiently discharged. Accordingly, when drive of the printing apparatus resumes, the heat storage of the respective motors becomes nearly zero. On the other hand, in a case where the power-off state is relatively short (for example, the power-off state continues for about 5 minutes), the heat of the respective motors is not sufficiently discharged. Accordingly, when the drive of the printing apparatus resumes, there is a possibility that the heat is still stored in the respective motors.
In order to solve such a problem, in the printing apparatus, when a user operates a power switch (operation unit) to turn the power source off, the heat storage of the respective motors at the power-off time is stored in a nonvolatile memory as operating heat storage, and then the power source becomes turned off. Afterward, when the user operates the power switch again to use the printing apparatus (that is, to turn the power source on), the operating heat storage read from the nonvolatile memory is set to a reference heat storage (an initial value). On the basis of the reference heat storage, heat storage of the respective motors at the time of resuming the drive of the printing apparatus is calculated (for example, see JP-A-2003-79187).
Accordingly, if the power source is turned on in a state where a period of time (referred to as an interrupt period of time) after the power-off until the power-on is relatively short (for example, the interrupt period of time is about 5 minutes), operating heat storage read from the nonvolatile memory is just slightly much than actual heat storage (hereinafter, referred to as “actual heat storage”) of the respective motors immediately after the power source is turned on. Therefore, in the printing apparatus disclosed in JP-A-2003-79187, the emission heat controlling is performed when the actual heat storage generated by the drive of the respective motors is equal to or larger than the heat storage threshold value in a case where the interrupt period of time is short.
However, in the printing apparatus disclosed in JP-A-2003-79187, as the interrupt period of time is longer, the reference heat storage (=operating heat storage) of the respective motors at the time of turning the power source on becomes considerably different from the actual heat storage of the respective motors. Therefore, in a case where the interrupt period of time is relatively longer, the calculated heat storage of the respective motors exceeds the heat storage threshold value even though the actual heat storage of the respective motors does not yet exceed the heat storage threshold value. For this reason, the emission heat controlling may be performed at erroneous time. In this case, the performance of the emission heat controlling may result in printing start failure or slow printing speed, contrary to a user desire to perform speed printing.
In a printing apparatus mounted with a RTC (Real Time Clock) for clocking time even in the power-off state by feeding a power source from a battery or the like provided therein, the interrupt period of time is exactly calculated. Accordingly, it is possible to exactly calculate the amount of discharged heat of the respective motors during the interrupt period of time. However, if the printing apparatus is provided with the RTC, an element of the printing apparatus has to be added, thereby increasing manufacturing cost.